1. Field of the Invention
The present invention relates to the field of image processing, and more particularly relates to a method for establishing an evaluation standard parameter and method for evaluating the quality of a display image.
2. Description of Related Art
Display as the friendly interface of human-computer exchange of information can output in formation accurately, intuitively, and clearly. When the display is sold as an electronic product, the quality of the display image becomes one of the important buying determinants of consumers. The image quality is determined by the brightness, the color shift, the clarity, and other relevant parameters. Therefore, the evaluation of the quality of the display image is important to be considered in the contents of the display development and design. Because the information of the display can be observed directly by the human eye, and its evaluation standards are different for different environments and applications. In recent years, with the rapid increase in the number and diversity of the various display technologies, it increases the requirements for the quality of the display image.
In the prior art, the evaluation the quality of the image uses JND criteria (Just Noticeable Difference). It requires to use a visual perception experiment based on the psychophysical method to determine a JND critical image, specifically as follows: displaying simultaneously two images in parallel on the monitor each time, wherein one is for an original image and the other is a test image. An observer requires selecting the image that the observer think that the color shifts are obvious in the two images. At first, the color shift difference between the test image and the original image is very large. The observer can easily distinguish the two images. If the selection is correct, it reduces the color shift difference, between a next test image and the original image. If the selection is wrong, it increases the color shift difference between a next test image and the original image. Repeat the above process. When the color shift difference meets certain condition, the corresponding test image is the JND critical image. For evaluating a subsequent image, it is the reference base.
However, because the different technical proficiency of the observer, the results of the above evaluations by human eye of the observer maybe different. Even if it is evaluated by the same observer, because of the actual state, the different time, the viewing angle of the display, observed from different light conditions, it leads to that the subjectivity will enter the evaluation resulting in the inconsistency of the evaluation. In addition, the level of awareness of the severity degree of the color shift in the display by the observer will change with different image brightness and ambient light conditions.
As stated above, because the evaluation involves the subjectivity, it is difficult to give an objective and fair evaluation in display design, development and consumer.